Commercially and clinically, silicone hydrogel contact lenses are a popular alternative to conventional hydrogel contact lenses (i.e., hydrogel contact lenses that do not contain silicone or silicone-containing ingredients). The presence of hydrophobic ingredients, such as siloxanes and other hydrophobic reactive ingredients, in silicone hydrogel contact lens formulations is believed to contribute, at least in part, to the frequent occurrence of clinically ophthalmically unacceptable surface wettabilities associated with the development of new silicone hydrogel contact lenses. For example, a silicone hydrogel contact lens can be determined to have a clinically ophthalmically unacceptable surface wettability if visually identifiable (identifiable under magnification) “non-wetting spots” are observed on a lens surface by an eye care practitioner using conventional techniques, such as slit lamp examinations. A non-wetting spot appears as a discontinuity or disruption in the lens wearer's pre-lens tear film present on the anterior surface of the silicone hydrogel contact lens provided on the eye. A non-wetting spot differs from a dry spot in that a non-wetting spot is a spot on a surface of the contact lens that does not become covered with tear film, even after the lens wearer blinks. In contrast, a dry spot as understood in the art, is a spot on a surface of the contact lens that is covered with pre-lens tear film after a blink and where the pre-lens tear film is disrupted or broken after an amount of time. It is believed that non-wetting spots may be attributed to increased amounts of hydrophobic lens material, such as siloxanes, present at the location of the non-wetting spots, compared to other regions of the lens surface that are wettable with pre-lens tear film.
The commercial manufacture of silicone hydrogel contact lenses frequently includes one or more washing steps using volatile organic solvents, such as alcohol, to remove unreacted or partially reacted chemicals, especially hydrophobic chemical ingredients, from the polymerized lens bodies prior to packaging. This is frequently referred to as an extraction process to remove extractable material from the polymerized silicone hydrogel contact lens product. Following extraction the lens is then rinsed and hydrated using an aqueous solution. The use of volatile organic solvents facilitates removal of a component of the polymerized silicone hydrogel contact lens that has poor solubility in aqueous solutions or water. However, the use of volatile organic solvents presents safety risks to contact lens manufacturing sites, and can be associated with increased costs of goods.
In addition to extracting with volatile organic solvents, a variety of additional manufacturing techniques have been employed to make silicone hydrogel contact lenses having clinically ophthalmically compatible lens surfaces. For example, some silicone hydrogel contact lenses are treated with plasma to form a hydrophilic lens surface; some silicone hydrogel contact lenses are formed from a polymerizable lens formulation containing a hydrophilic polymeric internal wetting agent, such as polyvinyl pyrrolidone (PVP); some silicone hydrogel contact lenses are formed using polar resin contact lens molds instead of non-polar resin contact lens molds, and the lenses do not contain a hydrophilic polymeric internal wetting agent in the polymerizable lens formulation, and are not subject to plasma treatment; and some silicone hydrogel contact lenses are formed in non-polar resin molds and are provided with ophthalmically compatible lens surfaces based on chemical reactivity properties of the chemicals in the polymerizable lens formulation.
Recently silicone hydrogel contact lenses have been produced and prescribed as daily disposable contact lenses (e.g., the 1-DAY ACUVUE TRUEYE (launched in the United Kingdom in 2008) and CLARITI 1-DAY (launched in the United Kingdom in November 2009); both apparently available in Europe. The lens material for 1-DAY ACUVUE TRUEYE contact lenses has a US Adopted Name (USAN) of Narafilcon A, and now more recently, Narafilcon B. The lens material for CLARITI 1-DAY contact lenses has a USAN of Filcon II 3. It has been published that the TRUEYE (Narafilcon A) contact lenses have a water content of 54%, an oxygen permeability (at −3.00 D, center, non-edge corrected) of 100 Dk; an oxygen transmissibility (10−9 at −3.00 D) of 118 Dk/t, a modulus of 0.66 MPa, and are associated with a wetting agent/process. It has been published that the CLARITI 1-DAY contact lenses have a water content of 56%, an oxygen permeability (at −3.00 D, center, non-edge corrected) of 60 Dk; an oxygen transmissibility (10−9 at −3.00 D) of 86 Dk/t, a modulus of 0.50 MPa, and are associated with a wetting agent/process.
As understood in the industry, a daily disposable contact lens is a contact lens that is removed from its sealed, sterilized package (primary package) produced by a contact lens manufacturer, placed on a person's eye, and is removed and discarded after the person is done wearing the lens at the end of the day. Typically, the duration of lens wear for daily disposable contact lenses is between eight and fourteen hours, and they are not cleaned or exposed to cleaning solutions prior to placement in the eye since they are sterile prior to opening the package and then disposed. Thus, a daily disposable silicone hydrogel contact lens is a disposable silicone hydrogel contact lens that is replaced daily. In contrast, non-daily disposable contact lenses are disposable contact lenses that are replaced less frequently than daily (e.g., weekly, bi-weekly, or monthly). Non-daily disposable contact lenses are either removed from the eye and cleaned with a cleaning solution on a regular basis, or are worn continuously without removal from the eye.
In addition to modality differences, the manufacture of daily disposable contact lenses can require changes in chemicals used to make the lenses, changes in manufacturing processes, or both, compared to non-daily disposable contact lenses in order to produce a commercially acceptable number of lenses in a cost-effective manner.
Based on the popularity of silicone hydrogel contact lenses, there continues to be a need for new silicone hydrogel contact lenses that are ophthalmically compatible.
Some documents describing silicone hydrogel contact lenses include: U.S. Pat. No. 4,711,943, U.S. Pat. No. 5,712,327, U.S. Pat. No. 5,760,100, U.S. Pat. No. 7,825,170, U.S. Pat. No. 6,867,245, US20060063852, US20070296914, U.S. Pat. No. 7,572,841, US20090299022, US20090234089, and US20100249356, each of which is incorporated in its entirety by reference herein.